Non-Patent Document 1: Masato Tanaka, RFID by using fabric antenna, Proceedings of IEICE General Conference 2006, B-1-173, March 2006
Non-Patent Document 2: Wearable microstrip antenna for satellite communications, IECE Transaction on Communications, vol. E87-B, no. 8, August 2004
Patent Document 1: JP 2002-352199 A
Patent Document 2: JP 2005-236858 A
In recent years, attention is focused on ubiquitous computing as the information environment in which computers exist everywhere in life and society and computers autonomously work together and operate to strongly support the everyday life of people, and this is partially realized.
In the ubiquitous computing, a computer can perform processing as automatically working together with other computers while referring to personal information and the like stored in networks, as necessary, although their presence is not perceived. For example, in addition to car navigation systems and the like, which search for routes and information about neighboring areas linked with VICS information, there are wearable computers that can be “worn” by combining a computer with a garment.
In addition, in a ubiquitous computing-oriented near future society, wireless communications are essential between computers.
For example, the above-described wearable computer may be an exercise monitor device integrated into a garment worn by a person, or an RFID tag device attached to various goods. Although light waves, radio waves, electromagnetic coupling, and so on can be considered to be a wireless communication means used in these devices, it can be thought that use of radio waves is the optimum in consideration of communication ranges, efficiency, etc.
On this occasion, antennas are indispensable to conduct communications according to radio waves. However, because it is not considered in typical antennas that antennas are freely deformed for use, a rigid material of relatively high shape retention is used for them. Furthermore, as a reason for using a rigid material of high shape retention, this is also due to avoidance of structural deformation that might lead to changes in the resonance frequency because antennas use resonance phenomena.
On the other hand, as the antenna for use in the above-described wearable computer, one of its conditions is deformable.
FIG. 15 is a cross section depicting an RFID according to a fabric microstrip antenna used in the Non-Patent Document 1, which uses an IC chip operated in the 2.45 GHz band.
In the drawing, in a fabric antenna 1, conductive woven fabric is used for an antenna patch 2 and a ground plane 3, and felt is used for a dielectric substrate 4. Furthermore, the polarization is right-handed circular polarization. For feeding power to the antenna, a rear pin feed method by an ultrasmall connector 5 is adopted, and an insulating layer through wiring 6 connects between the antenna patch 2 and the ground plane 3.
The conductive woven fabric used for the antenna patch 2 and the ground plane 3 is fabric used as an electromagnetic interference shielding material, and the fabric uses polyester thread each of which is treated with a metal coating. In addition, commercially available felt is used as the felt for the dielectric substrate 4, and the ultrasmall connector 5 is a publicly known connector for use in a mobile telephone.
Furthermore, as the structure of a so-called wearable antenna like this, in addition to the above-described Non-Patent Documents 1 and 2, for example, these techniques are considered: the technique in which as a wireless communication antenna having flexible properties that the antenna is worn mainly on the curved surface of a human body, an object, or the like and relatively freely deformed, an antenna of a reader/writer communicating with an RFID tag in a noncontact manner is integrally disposed on a bendable band by providing a catch on both end portions of the band, whereby the antenna is worn on the wrist to communicate information with the RFID tag attached to a package in a noncontact manner, packages can be loaded and unloaded with the antenna worn without putting on and off the antenna every time, even though an operator is driving a track or writing a delivery slip by hand, and thus the burdens of loading and unloading packages and management are reduced (see the Non-Patent Document 1); and the technique in which an antenna is formed in one piece with a strap mountable on a cellular telephone and the like, as a material for an antenna core, such a core material is used that the core material is formed of soft magnetic powder and an organic binder and is rich in flexibility and rubber elasticity, this core material is arranged on both sides of the strap, and wire is wounded to configure the antenna, whereby the antenna can be used in frequency bands lower than the AM band, and the antenna has high gains and impact resistance as well as flexibility and elasticity (the Non-Patent Document 2).